An X-ray CT apparatus is a diagnostic imaging apparatus that emits X-rays, detects the X-rays which have penetrated through a subject, and reconstructs the image of the subject from the projection data showing the intensity of the detected X-rays.
As a scanning method using the X-ray CT apparatus, for example, dynamic volume scanning and helical scanning are well known.
Volume scanning refers to a method in which a plurality of detectors (for example, several hundred rows) are provided, and by rotating these detectors around a fixed subject, for an organ approximately the size of a heart, 3-dimensional data thereof can be acquired with one scan. Moreover, dynamic scanning refers to a method in which movement of the subject is photographed by performing X-ray scanning on the subject into which a contrast agent is injected. Dynamic volume scanning refers to the combination of these methods.
Moreover, helical scanning refers to a method in which while scanning is performed with detectors that are continuously rotated at a high speed, by simultaneously moving the bed on which the subject is placed at a constant speed, a plurality of cross-sectional scans are completed in a short period of time.
Moreover, a well-known method referred to as the dual energy method can be used in combination with these scanning methods.
This method sequentially performs, with respect to the same site of the subject, X-ray scanning with a high tube voltage and X-ray scanning with a low tube voltage, generating a difference image based on the two X-ray image data obtained using X-rays of different radiation quality.